1. Technical Field
The present invention relates to a virtual image display apparatus, such as a head-mounted display worn around the head for use.
2. Related Art
In recent years, as a virtual image display apparatus that allows formation and observation of a virtual image, such as a head-mounted display, there is, for example, a proposed scanning image display apparatus in which the retina of each eye is so scanned with image light that an image is projected onto the retina (retina projection display apparatus), and the apparatus allows continuous observation of video images and character information by tracking motion of the eye and changing the scan direction accordingly (see JP-A-2009-122550). There is also a proposed scanning image display apparatus in which a diffraction optical element is disposed in the optical path to adjust light fluxes in such a way that the angle of divergence of a light flux in a specific direction is greater than those of light fluxes in the other directions for reduction in loss of light from a light source (see JP-A-2007-199251).
However, in JP-A-2009-122550, which always tracks motion of the eyes and provides video images in accordance with the tracking result, even when the wearer, for example, temporarily averts the eyes from video images, the video images remain visible irrespective of the motion of the eyes, which may bother the wearer in some cases. On the other hand, in JP-A-2007-199251, in which a diffraction optical element is disposed in the optical path or the diffraction optical element is followed by another optical system, the portion of the apparatus in front of the eye tends to be large and heavy. Further, in this case, it is sometimes difficult to achieve a see-through configuration that allows image light that forms a virtual image to be superimposed on outside light that is light from the outside.